As we near the start of flu season, beware: Many of the city’s top hospitals pose a serious hazard to your health, because many of their nurses and other care personnel aren’t vaccinated — and don’t have to be.

To protect both workers and patients, at least 90 percent of health-care personnel should be vaccinated.

At Mount Sinai, it’s just 58 percent; at Maimonides Medical Center, 55 percent; at New York Hospital-Queens, 60 percent.

Two years ago, the public-health nonprofit where I work, The American Council on Science and Health, sent HHC a petition signed by 35 nationally renowned experts in infectious disease, demanding it implement a mandatory vaccination policy.

We got nowhere.

We then appealed to the state Department of Health, which said it had such a policy under consideration. But, sigh, DOH caved to union resistance, and merely adopted an optional “vaccinate or mask” policy.

The Centers for Disease Control report that there is no evidence that “mask use by either infectious patients or health-care personnel prevents influenza transmission.”

In other words, the Department of Health is promoting a flu-prevention policy that doesn’t prevent the spread of flu.

And some of those deaths are preventable — people who caught the flu while hospitalized for something else. Hospital patients are among the most vulnerable to the severe (even lethal) complications of influenza.

Widespread immunization campaigns can reduce this frightful toll. Seasonal flu vaccines can reduce morbidity by 60 to 90 percent; they’re easily the most effective method to prevent transmission of the virus.

Prevents the virus from spreading to patients, including those with weakened immune systems.

Promotes “herd immunity,” making it less likely that the virus can spread to those who can’t be vaccinated or for whom the vaccine doesn’t “take.”

Ensures that the health-care workforce remains functional even in the event of a massive flu outbreak.

In short, this is a core safety practice for public health. It’s obscene that HHC refuses to mandate annual flu vaccination as a condition of initial and continued employment and/or professional privileges. (The only permitted exemptions should be for documented medical conditions.)

Yet the unions for nurses and other hospital workers resist, citing reasons from “freedom of choice” to religious objections to fear of side-effects.

Sorry:

No religion gives you the right to put the sick at added risk of disease.

Freedom of choice means the freedom to find other work if you won’t be vaccinated to protect yourself and others — not the freedom to threaten others’ health.

If you can’t see that the benefits of vaccination outweigh the tiny risk of side-effects, you don’t belong working in a hospital.

Union opposition is potent.

It took vaccine expert (and ACSH trustee) Dr. Paul Offit and his team a full six years to finally implement the Children’s Hospital of Philadelphia’s “Get vaccinated or get out” policy, ultimately firing only nine out of 9,300 CHOP employees.

But it can be done, and must be done.

Physicians and other health-care providers are bound by three key ethical duties: “To do good or to do no harm,” “To put patient interests first” and “To protect the vulnerable.”

To avoid or ignore these clear duties is unprofessional and worse, is detrimental to public health.

Yes, a mandatory-vaccination is coercive. So what? Voluntary approaches don’t work, and protecting the public health justifies such coercion.

Every hospital should tell its workers: “You may choose not to be vaccinated — or to work in this hospital with sick patients. Not both.”

Dr. Gilbert Ross is the medical and executive director of The American Council on Science and Health.